The disclosure relates to a method for axis correction in a processing machine and to a corresponding processing machine, a corresponding computer program and a corresponding computer program product.
Although reference is primarily made below to printing machines, the disclosure is not restricted to this, but is directed to all types of processing machines with driven and non-driven axes or rollers. The disclosure can be used in particular in printing machines such as newspaper printing machines, job printing machines, intaglio printing machines, packaging printing machines or security printing machines as well as in processing machines such as bagging machines, envelope machines or packaging machines, for example. The continuous web may be formed from paper, cloth, cardboard, plastic, metal, rubber, in film form etc.
In processing machines, in particular printing machines, material in sheet form or in the form of a continuous web is moved along driven axes (transport axes), such as drawing rollers or feed rollers, for example, and non-driven axes, such as deflecting rollers, guide rollers or cooling rollers, for example. The material is processed simultaneously by means of usually likewise driven processing axes, for example is printed, stamped, cut, folded etc.
The processing and transport of the material influence both a web tension and a processing register, for example a color or longitudinal register. In conventional processing machines, it is therefore usual to control the processing register and/or the web tension. In printing machines, longitudinal and/or lateral registers are controlled in order to achieve an optimum print result.
In the prior art, acceleration and braking operations are included in the web tension control and the register control only to a small degree, for example by means of taking into consideration a permanently stored ramp-up curve of the processing axes or by means of taking into consideration permanently stored constant web tension setpoint value changes.
One disadvantage of these measures is the fact that, in the event of acceleration operations, errors in the register and in the web tension are not taken into consideration on the basis of the present acceleration value, but merely on the basis of a permanently stored acceleration value, for which reason all errors occurring need to be compensated for as control difference of a web tension or register controller.
DE 101 35 773 A1 describes feedforward control for the time of a change in role, wherein parameters of the new role such as, for example, moisture, thickness, stress-strain characteristic and absorption capacity for moisture are taken into consideration.
DE 10 2007 037 564 describes the determination of feedforward control values for the register control during a change in speed taking into consideration the moment of inertia of non-driven rollers.
In EP 0 709 184 A1, feedforward control values for different printing speeds are determined by measurement runs. These are relatively time-consuming and furthermore result in printer's waste.
One disadvantage of the known solutions is the fact that the basic model used as the basis for the calculation of feedforward control values from the parameters respectively to be taken into consideration only incompletely simulate reality and also change the actual machine and material data on the basis of physical influences such as temperature in the dryer, ambient temperature, for example, during the processing, which results in further deviations. No damping-dependent proportion of the material web which has a strong influence on the web tension and the register during acceleration phase, particularly in the case of film-like printed materials, is taken into consideration either, for example.
There is therefore the problem of specifying an improved method for axis correction during a change in speed.
This problem is solved by a method for axis correction, a processing machine, a computer program and a computer program product having the features of the independent patent claims. Advantageous developments are the subject matter of the dependent claims and the following description.
A processing machine according to the disclosure, in particular a shaftless printing machine, has at least one axis for processing and/or transporting a material, at least one detection device for detecting a processing parameter and at least one controller device for calculating a controller output variable or manipulated variable for axis correction of the at least one axis using the detected processing parameter. The detected processing parameter may be in particular a register position or a web tension or the corresponding deviations or errors, wherein in the event of a register and/or web tension error being detected, a register and/or web tension correction is then implemented as axis correction. The controller device is designed to implement a method according to the disclosure, namely to determine feedforward control output values for the feedforward control of the axis correction during a second change in rotation speed of the at least one axis using observation of the controller output variable during a first change in rotation speed. The method is implemented iteratively. Since with the first run of the method there are not yet any adapted feedforward control values available, the associated feedforward control values (or the compensation values to be explained further below) can be determined on the basis of a model, for example, or can be taken from a stored formula, as will be described further below. A suitable model is, for example, one of those described above in the description of the prior art.
In addition, it is possible to determine second feedforward control output values on the basis of a model using known machine or material parameters which, in addition to the feedforward control output values, are used for the feedforward control of the axis correction and, when totaled, for example, form total feedforward control output values.
Although the disclosure will be described below essentially with reference to the observation of the controller output variable, the observation of the processing parameter is also always intended thereby. For example, in the case of purely a P register controller, the controller output variable would be proportional to the register error, for which reason in this case the observation of the register error is equivalent to the observation of the controller output variable. Expediently, the register error determined respectively at the axis is observed as register error. Generally, feedforward control output values for the feedforward control of the axis correction can be determined during a subsequent change in rotation speed of the at least one axis also using an observation of the controlled variable (feedback variable) or the control deviation during a proceeding change in rotation speed.
Advantageously, the feedforward control of all relevant axes of the processing machine is performed. In particular, in order to control or to adjust the web tension in a web tension section, feedforward control of the clamping points delimiting the web tension section is performed and, in order to control or adjust the register of a processing axis within a web tension section, feedforward control of the processing axis and/or the clamping points which delimit the web tension section is performed. If the processing axes at the same time ensure the transport of the material and are therefore in the form of clamping points, in order to regulate or adjust the register, feedforward control of this processing axis itself is performed.
Typically, additive angle offsets, additive speeds and/or multiplicative speed factors (so-called fine tuning, gear ratios) are subjected to feedforward control as feedforward control output values.